Mexican Macaroni Casserole

1. Preheat oven to 375 F.
2. Heat the oil in a large skillet over medium high heat. Add the mushrooms and bell pepper. Sauté until the veggies are soft, about 3 minutes.
3. Add the spinach to the skillet and season with salt, pepper and garlic powder. When all the spinach has wilted down, remove the pan from the heat. Set to the side.
4. Put a large pot of water on to boil for the pasta.
5. Meanwhile, melt the butter over medium heat in a 3 quart sauce pan. Then whisk the flour into the melted butter and cook, while whisking for about 3 minutes.
6. Slowly whisk the milk into the flour butter mixture.
7. When the milk is hot, whisk in the cheeses.
8. When the cheeses have melted, stir the Rotel chilies and tomatoes into the sauce. Remove the pan from the heat and set to the side.
9. When the water comes to a boil, add a generous amount of salt and the pasta. Cook the pasta for only 6 minutes. Then drain the water off the pasta and keep the pasta in the pot.
10. If your chicken is cold, then just heat it through (put it in the microwave for a minute or two, just until warmed).
11. Stir the cooked veggies, cheese sauce, chicken and scallions into the pasta.
12. Pour the pasta into about an 8 x 11 x 2 inch casserole dish, top with the crushed tortilla chips, and bake for 30 minutes.